ation is a widespread post-translational modification of tyrosines found in all animal cells containing a Golgi system. In fact, approximately 1% of the tyrosines are sulfated in tissue in the rat. Despite this observation, only 24 unique protein sequences containing tyrosine sulfate have been described. The aim of this project is to analyze the amino acid sequences surrounding know tyrosine sulfation sites to determine the characteristics of this site and, therefore, to identify more candidates of sulfation. The specific goals are: 1. to identify the characteristics of sulfated tyrosines which distinguish them from non-sulfated tyrosines. These characteristics include the number and distribution of amino acids, as well as the possible secondary structural features in the vicinity of the tyrosine. 2. to identify proteins with probable tyrosine sulfation sites from the Swiss Protein data base. 3. to determine sequence similarities among the set of known proteins in the vicinity of the sulfation site. Identification of new protein sulfation sites may be essential for the understanding of the function of these proteins and will lead to a better understanding of the function of tyrosine sulfation.